Contact printer



May 2, 1967 c. o. CARLSON ETAL 3,316,825

CONTACT PRINTER Filed May 26, 1964 5 Sheets-Sheet l lnvenfars. Car/ 0. Car/son Benjamin ESc/rerr Ivan l. Rondas May 2 1957 C. o. CARLSON ETAL 3,316,825

CONTACT PRINTER 5 Sheets-Sheet 2 Filed May 26, 1964 Inventors. Uur/son Il. Benjamn FSC/:err

- /van V Rondas carl. a

The/'rAf/arneys.

May 2 1967 c. o. CARLSON ETAL 3,316,825

CONTACT PRINTER 5 Sheets-Sheet 3 Filed May 26, 1964 /n venfors. Carl. 0. Car/son Benjamn ESC/ferr /vcm l/. Randos if M55?? May 2, 1967 c. o. CARLSON ETAL 3,316,825

CONTACT PRINTER 5 Sheets-Sheet 4 Filed May 26, 1964 May 2, 1967 c. o. CARLSON ETAL 3,316,825

CONTACT PRINTER Filed May 26, 1964 5 Sheets-Sheet 5 Car/ 0. Car/son Benjamin E Scherf /van V Rondas United States Patent O 3,316,825 CONTACT PRINTER Carl 0. Carlson, Los Angeles, Benjamin F. Scherr, Hawthorne, and Ivan V. Rondas, Compton, Calif., assgnors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed May 26, 1964, Ser. No. 370,314 4 Claims. (Cl. 9573) This invention relates to a photographic contact printer and, more particularly, to an improved contact printer for printing high resolution images by establishing a high degree of contact between the surfaces of a master negative and a film on which the images are to be printed.

Microimages having an equivalent resolution of 1,000 lines per millimeter or better are readily produced using known techniques and apparatus, for example, as disclosed in a copending United States application Ser. No. 111,759, filed on May 22, 1961, now Patent No. 3,185,- 026, inventors Carl O. Carlson et al., and assigned to the same assignee as this application. The copending patent application teaches that very high resolution microimages can be formed by projection onto a photometachromic (hereinafter called photochromic) emulsion that is coated on a glass plate. Also the copending application teaches that permanent copies of the microimages formed in the photochromic coating can be contact printed onto a high resolution, conventional photographic ilm by using a contact printer having a resilient or felt-like support. The resilient support provides for transmitting only a normal, evenly distributed pressure to the interface between the two coatings there-by tending to cornpensate for any non-tiatness of the surfaces of the emulsion coatings which surface unevenness is a property of emulsions, especially when supplied as coatings on films. While, with care, high resolution contact prints can thus be made by using such a resilient support for the film, when it is desired to more easily and consistently contact arrays of high resolution microirnages onto conventional photographicl film, ay more convenient and reliable manner of obtaining a high degree of intimate contact between the coatings is required. Since the degree of resolution in the contact print is related to the degree of contact between coatings, the measure of uniformity of contact can be noted by inspecting the lack of or the number of light interference fringes present at the interface of the coatings. The spacing between coatings is directly related to the number and sp-acing of fringes formed, and is further related to the unevenness of the iilm coating. Thus, optimum contact, i.e., perfect contact, refers to the condition when no light interference fringes are formed over the interface of the contact surfaces. `It is t-o vbe noted that although a contact print with acceptable resolution could -be produced when a few widely spaced interference fringes are present, the contact prints are greatly degraded when many fringes are present. It has been found that the fringe regions are produced when pockets of air have been captured around clumps of emulsion at the time initial contact was made, and that the fringes -or the fringe regions can be reduced by one or more of the steps of applying more pressure to the contacting surfaces, removing air from Ibetween the surfaces before applying pressure, and/or waiting after pressure is applied for any air that might be entrapped between the surfaces to leak out or be absorbed by the material to thereby assure better contact ybefore exposing the iilm. The first approach, that is the use of more pressure to acquire more intimate contact, is impracticable Ibecause there is a tendency to break the master plates as larger pressures are applied. The second approach, removal of air before applying pressure, requires a vacuum system which materially complicates the ICC design and which is better avoided if possible. The third approach, the waiting for the bubbles of trapped air to dissipate, while generally helpful, provides no guarantee that the time delay will improve the contact, inasmuch as it could happen that an optimum contact has been formed around the air pocket cutting off a means for the air to escape. It should -be noted that -better results are obtainable in making contact prints onto photographic coatings applied on glass plates, due to the improved llatness yand parallelism of the glass substrate, but the same general effects -occur even there in trying to establish optimum contact between the coatings. It has also been suggested that a matching refractive index liquid be placed between master and copy to eliminate the interference -ringes or that a `ne grit be placed therebetween to make the fringes so numerous as to be unresolvable. However, this approach does not prevent the images from ybeing undercut Iby diffused illumination or prevent diffraction eiects with semi-specular or specular illumination from blurring the microimages at points Where master and copy fail to Ibe in optimum contact. It should thus be clear that in order to transfer the maximum amount of very fine-line information from the master to the copy, optimum or near optimum contact should be produced at the interface between coatings.

It has been mentioned above that optimum contact is achieved between the two coatings when no interference fringes are noticeable at the interface. It should be noted that interference fringes are not noticeable under two conditions: the first is when the spacing between the coatings is less than one-quarter wavelength and the second when the spacing is relatively large so as to make the interference fringes unresolvable. However, when the spacing is between these two limits and a red light of narrow bandwidth is used to illuminate the coatings, light and dark patterns are alternately formed. It has thus been observed that acceptable high resolution is produced in contact printing when the spacing between coatings is equal to no more than four wavelengths, which spacing is measured by counting the interference fringes from a region of optimum contact in the proper manner as each continuous dark area represents a fixed spacing between coatings. Acceptable high resolution in a contact print is accomplished for the purposes and intent of the present invention when a six point type font of characters which has been reduced about 200 diameters onto a master, is contact printed onto a photographic hlm, and the characters recorded or printed in the contact prints can be resolved with proper viewing equipment, for example.

A primary object of this invention is, therefore, to provide an improved contact printer that can make contact prints having high resolution `by establishing optimum or near -optimum contact between coatings on a master and a photographic iilm in a rapid and reproducible manner.

Another object of this invention is to provide a pressure plate for pressing a photographic film against a master which pressure plate initially applies a pressure to a small area on a photographic member to place the coatings opposite the pressure area in contact and then cause the area in contact to gradually increase outwardly to thus even out the surface of the coatings and prevent the formation of air pockets.

The primary feature of the invention is a contact printer with a pressure member provided with a curved surface that initially applies pressure at only a very small area on a photographic lm to press it against a master negative that is supported by a relatively rigid, transparent back-up plate. Since the initial contact area is small, a very high pressure is produced, and the high points in the Iilms coating are effectively squashed so that the valleys as well as the high points in the films coating are placed in intimate contact with the coating on the master. As the force ap- Patented May 2, 1967' plied by the pressure plate increases, more of the films coating comes into contact with the master, in turn, squashing more of the high points, and forcing air outwardly from between the film and master, preventing the formation of air pockets. When intimate contact is formed over the microimage area on the master that is to be printed, the film is exposed to light having the proper specularity. The invention also has a feature that safely separates the film from the master so that another portion of the film may be exposed.

Other objects, advantages and features of the present invention will become apparent from consideration of the following description when taken in conjunction with the appended claims and the drawings wherein:

FIG. 1 shows a contact print as produced on a photographic film by a master negative containing over 1200 high resolution microimages;

FIG. 2 is a greatly enlarged pictorial view of a fragment of the master negative and support therefor as used to print the contact print shown in FIG. l;

FIG. 3 is an exaggerated enlarged section of a fragment of an unexposed flexible photographic lm showing a typical emulsion clump or high point protruding above the normal surface of the emulsion coating;

FIG. 4 is a section :Showing the pressure plates of a step-and-repeat contact printer making initial contact between the emulsion coatings at the center of the master negative and the film;

FIG. 5 shows the pressure plates of FIG. 4 when full contact is made between the emulsion coatings;

FIG. 6 is a pictorial view of an automatic step-andrepeat contact printer employing the pressure plates shown in FIG. 4;

' FIG. 7 is a side elevation partially in section of the contact printer shown in FIG. 6;

FIG. 8 is a plan view of the contact printer shown in FIG. 6;

FIG. 9 is a section of the contact printer taken on line 9-9 in FIG. 7 showing the film advance rollers;

FIG. 10 is another section of the printer taken on line 10-10 in FIG. 7 showing one of the film lifters; and

FIG. 11 is a schematic diagram showing the pneumatic lines and the control circuitry for controlling the automatic printing operation of the contact printer shown in FIG. 6.

Referring to the drawings, FIG. 1 shows one of the high resolution contact prints of microimages that is made in accordance with the teachings of this invention. The contact print shown has an array comprising 50` columns and 26 rows of high resolution microimages 12 formed on a flexible photographic film, -approximately 21/2 by 2 inches in size. Each microimage 12 represents a page (5 x 8 inches) of a book which has been reduced over 200 diameters, for example. Such a reduction readily provides 32 microimages to the inch in each row and microimages to the inch in each column. Thus, an array of over 1200 microimages is formed on the contact print and the resolution of each microimage -is suiieient so that the printing can be easily and clearly readable when the microimages are enlarged by a viewer specially designated to handle such small microimages.

. The contact print shown in FIG. 1 is made from a master 16, a fragment of which is shown greatly enlarged in FIG. 2. The master 16 contains an array of microimages 17 which is of the same size as microimages 12. The size of the master is, for example, 5 x 7 inches so that a wide border is provided around the array -of microimages 17. The resolution of the microimages 17 is sufficiently high to allow for some degrading during the contact printing process. It iswell known that there are a number of factors that contribute to -degrading the resolution of a contact print, )for example, such vfactors include: the degree of contact between coatings, the thickness of the coating, and the type of light exposing the coatings. The master 16 includes a rigid transparent base member such as a plate of glass 18 which has an optically polished surface coated with a photosensitive coating 19 in which the microimages 17 are formed. I-t should be understood that in -comparison to the thickness of the glass 18 which may be about s of an inch, the thickness of the coating 19, being only a few microns, is shown greatly exaggerated in the drawings. The coating 19 of photosensitive emulsion may be made of any of a number of well-known photochromic or Isilver halide materials. Photochromic material has no grain size and, therefore, the upper limit of resolution that can be recorded thereon is not even measurable through available optical systems. A silver halide material has been produce-d of such fine grain that the emulsion is able to record over 2,000 lines per millimeter. The above-mentioned application of Carlson et al. teaches how to make a master on a photochromic emulsion coating. The present application teaches how high resolu-tion contact prints can be pro- -duced from a master made of either a photochromic or silver halide emulsion coating.

Since the resolution of the microimages printed in coating 19 is inversely related to the coatings thickness, the coating 19 is coated as thin and even as practical on the glass backing 18. For example, an acceptable photochromic coating can be made as thin as 3 microns, and an acceptable silver halide coating can be made as thin as `6 microns. vSince the coating 19 is on the optically polished and hard glass surface, the variation in thickness is .relatively small, being less than one micron. The variation in Ithickness is primarily `due to the emulsion drying and shrinking.

Since microimages on glass are expensive and fragile to handle, copies .to be -generally disseminated and to receive a lot of handling should preferably be made on a flexible photographic film, such as the contact print shown in FIG. l. Referring to FIG. 3, there is shown an enlarged cross-section of a typical high resolution dexible photographic film 21. The high resolution film 21 has a Aflexible base made of, for example, cellulose acetate 22 coated with a silver halide emulsion coating 23. A silver halide emulsion coating is preferred because the microimages thereon can be lfixed or made permanent more readily than on a photochromic coating. However, due to limitations in the manufacturing process, when a silver halide coating is formed on a cellulose acetate film, the Iresultant coating 23 is relatively uneven in'comparison to the emulsion coating 19 on glass 18 which, as mentioned before, has a variation of less than one micron. As previously mentioned, the thickness of coating 23 is -greatly exaggerated in the drawing in comparison to the thickness of the cellulose acetate substrate 22. The cellulose acetate substrate has a thickness of about microns, but the coating 23 thereon has been observed to have peaks, for example, peak 24 formed by an emulsion clump which may be protruding several microns above the normal surface of the coating 23. Peaks, like the peak 24, are spaced irregularly in the coating 23. It becomes apparent, therefore, that when a relatively flat surface as forme-d on the masters coating 19 is pressed against an uneven surface as formed on the films coating 23, air pockets may be trapped in the valleys formed around t-he peak 42 unless precaution is taken during contact printing to prevent Ithis from occurring. Air pockets are detrimental in prin-ting very high resolution microimages because the emulsion coatings 19 and 23 are prevented from making optimum contact. As well understood in the art, spacing between emulsion coatings during contact printing forms diffraction patterns and interference fringes when the dilm 21 is exposed to light, resulting in a blurring of the microimages being printed. Since the microimages represent greatly reduced printed information, the air pockets could be large enough to blur out the words on half of a page, for example.

In addition, a space or air pocket between emulsion coatings `19 and 23 'can be formed around a dust particle.

This application teaches how Vto minimize the effects of peaks 24 and also dust particles in preventing intimate contact between coatings. But it should be noted that although the coatings can be squeezed around the dust particle, the blocking of the lig-ht by the dust particle could cause many Words to be blotted out of the page represented by the microimage. Therefore, care should be taken to remove any dust particles off the master and film.

Referring to FIG. 4, a cross sectional view illustrating the principle of the contact printer of the present invention is shown. The contact printer includes a pair of rigid pressure plates 31 and 32 that are made of a material such as aluminum, which has a relatively high modulus of elasticity in comparison to cellulose acetate, for example. The pressure plate 31 has a convex surface 33 that in the present embodiment is cylindrical, inasmuch as cylindrical surfaces produce smaller stress concentrations in the back-up plate than convex surfaces of other shapes. Since the convex surface 33 contacts the film 21, the surface 33 is polished by hand to remove tool marks so that the film is not scratched when it contacts the convex surface. The other pressure plate 32 has a concave surface 34 provided with an opening 36 for the passage of light rays employed to expose the film 21. On surface 34 and over the opening 36 is placed a flat, glass back-up plate 37, that is substantially larger than the opening 36. The back-up plate 37 is about 1A inch thick and provides a yieldable structural support for the master 16 placed thereon. It should be noted that if the glass plate 18 forming the base member of the master 16 (FIG. 2) has sufficient thickness and rigidity, then the back-up plate 37 would not be required. The master 16 is positioned with its coating 19 facing away from the back-up plate 37. A liquid having approximately the same index of refraction as the glass in the plate 37 and the master 16 is used to wet the interface therebetween and thereby provide a fringeless contact. The side of film 21 with the emulsion coating 23 is placed on the master 16. However, it is preferred not to use a liquid to wet the interface between the coatings 19 and 23 because as mentioned above the degree of intimacy between coatings can be checked after pressure is applied by inspecting the interference fringes. If the degree of intimacy is not acceptable, corrective action could be taken, for example, as by applying more pressure. When the pressure plates 31 and 32 are forced together by suitable means (to be described hereinafter), the convex surface 33 and the fiat, back-up plate 37 cause the emulsion coatings 19 and 23 to be forced together to contact initially within a narrow area (marked A in FIG. 4) at the center of the master 16. Because the initial area in contact is narrow, practically a line, a large pressure is produced on the few high points or peaks in the emulsion coating 23 that may be located within the contact area. The high pressure evens the surface, i.e., rolls out lor flattens the emulsion in the high points, so that the entire surface of the coating 23 within the area A is in intimate contact with the surface of the coating 19. As the force onsthe pressure plates is increased, ythe narrow contact area broadens outwardly on either side from area A flattening more of the high points, in turn. Air is forced outwardly from between the coatings so that air pockets are not formed. In the meantime, the central portions of the backup plate 37 and the master 16 bend in toward the concave surface 34 of pressure plate 32 as the force increases. In order to prevent high stress concentrations from being formed in the back-up plate 37, the concave surface 34 on the pressure plate 32 is shaped to intimately mate with convex surface 33. When full contact is made between the emulsion coatings 19 and 23, the pressure `plates 31 and 32, lm 21, master 16, and back-up plate 37 are in the position as shown in FIG. 5. It should be noted that when the two members 21 and 16 are pushed together at the center and thereby bowed,

as shown in FIG. 5, a closer contact is inherently obtained at the center than near the edges. Therefore, since the master 16 has large yborders around the array formed by the microimages 17, optimum contact is more readily obtained in the central portion of the master containing the microimages than if the borders were made smaller. The film is exposed in a manner to be described hereinafter, and then developed in a well known manner with a conventional fine grain developer.

It should be noted that the curvature on the pressure plates and the thickness of the coatings 19 and 23 and the master 16 and film 21, respectively, are shown greatly exaggerated for illustration purposes only. In practice, a curved or bowed surface whose shape conforms to that of an arc having a radius of about 30l feet has been found to be sufficient to produce intimate contact between emulsion coatings without placing undue stress on the back-up plate or master. It should be noted that such an arcuate surface only defiects the master about .010 inch in a span of as much as five inches.

Although great care should be taken to ensure that no dust particles become lodged between the coatings 19 and 23 and that all the peaks 24 in the emulsion coating 23 are flattened, the pressure plates 31 and 32 with the concave and convex surfaces 33 and 34 may be incorporated into a contact printer that automatically cycles through a printing operation, for example every six seconds, 'to consistently produce high resolution contact prints of microimages 12 on successive frames of a roll of film 21.

Referring to FIG. 6, a pictorial view is shown of a pneumatically operated step-and-repeat contact printer that is -capable of producing microimages 12 having a high resolution on a roll of the film 21. The contact printer is mounted on a `bench 41 which has a vertically disposed grill 42 on the backside thereof. Dust-free air passes through the grill 42 and across the contact printer to blow dust particles away from the printer. The contact printer includes a metal base plate 43 on which is mounted a film supply mechanism 44 that includes a feed reel 46 containing a roll of unexposed photographic film 21. Thevfilm 21 rolls off the reel 46 and passes through a printing section 48 to a film take-up mechanism 49 and onto a take-up reel 51. Also mounted on the base plate 43 are three timers S2, 53, and 54, and circuitry to control the automatic operation of the contact printer.

The feed reel 46 `in the film feeding mechanism 44 is mounted to rotate on a shaft 56 which is supported at its ends `by two vertical side plates 57 and 53 (FIG. 8), fixed to the base plate 43. A suitable brake means, such as a leaf spring 59, applies a braking force to the feed reel 46 so that the reel does not rotate freely on the shaft S6. The film 21, after leaving the feed reel 46, passes under a suitable guide roller 61 (FIG. 7) that is mounted to and fixed in relation to the side plates 57 and 58. The roller 61 guides the film '21 brushes 62 and 63. The brushes 62 and 63, being antistatic, prevent the formation of an electrical charge on the film `21, and clean olf any loose foreign particles that may be present on the upper and lower surfaces of the film 21 before it passes through the printing section 48.

The printing section 48 comprises a press having a rigid metal bed 64 that is fixed to the base plate 43 and a movable rigid metal head 74 that is accurately guided by four guide posts 91 (FIG. 8) to move toward or away from the bed 64. The bed 64 has an opening 66 (FIG. 7) that is aligned with openings 67 and 68 formed in the base plate 43`and lbench 141, respectively. Removably mounted on the top of the bed 64 is tbe pressure plate 32 with the opening 36 therein aligned with opening 66 in the bed 64. The pressure plate 32 is secured to the `bed 64 by side rails 72. The plate `32 can slide between the rails 72 and be removed from between the bed 64 and the movable head 74 by pulling on a knob 75. When the pressure plate 32 is removed, the backbetween a pair ofl up plate 37 and the master 16 `can be carefully positioned thereon and readily inserted as an assembly within the press. The back-up plate 37 is suitably held on the pressure plate 32 by members 73.

The pressure plate 31 with the convex surface is suitably fixed to the underside of the rectangularly shaped movable head 74, and the suitable means (previously mentioned) for pressing the plates 31 and 32 together here includes a pneumatic piston and cylinder assembly 76. The piston and cylinder assembly 76 has a cylinder 77, enclosing a piston (not shown) that has a connecting rod 78 (FIG. 7) protruding sfrom the cylinder. The cylinder 77 is suitably mounted on a horizontal mounting plate 79, with the connecting rod 78 protruding downward through a bore 81 (FIG. 7) formed in the mounting plate 79, so that the end of the connecting rod 78 can be threaded into the movable head 74. The mounting plate 79 is rigidly supported over the movable head 74, at one end, by the two side plates 57 and 53 and transverse plate 82 (FIG. 7), and, at the opposite end, by two side plates 83 and 84 (FIG. 8) and -a transverse plate 86. The mounting plate 79, side plates 57, 58, 83 and l84, and transverse plates 82 and 86 are made of metal and are bolted together to provide a rigid pressure frame for the press.

The piston and cylinder assembly 76 forces the head 74 down toward the bed 64 when a four-way solenoid operated valve 87 pipes compressed air to a tube `88. Conversely, the head 74 moves up when compressed air is piped to a tube 89 by the valve 87. Tubes 88 and 89 communicate with opposite ends of the cylinder 77. As the head 74 moves up and down, it is guided by four guide posts 91, and a journal bearing contact is formed between the posts 91 and the head 74 so as to eliminate any horizontal motion between the film 21 and the master 16 when contact is made.

The film 21 passes through suitable film lifters 92 and 93 (FIG. 7) disposed on opposite sides of and mounted on the movable head 74. Since the film 21 makes a high degree of contact with the master 16, the function of the film lifters is to lift the Ifilm perpendicularly and safely ofi the master y16 as the head 74 rises and before the take-up mechanism 49 advances the film. The take-up mechanism 49 advances the film 21 as the head 74 rises. This action of the take-up mechanism 49 is controlled by a lever 94 linking the take-up mechanism 49 to the movable head 74. When the head 74 moves, the lever 94 rocks about a pin 96 fixed to the side plate 83 (see FIG. 8). The lever 94 rocks about the pin 96 because one end of the lever 94 has a slot 97 that engages a pin 98 fixed to the head 74. The other end of the lever 94 has a gear sector 99 that engages a pinion gear 101 fixed to one end of a shaft 102 which is bearing mounted to the side plate 83 (see FIG. 9). On the other end of shaft 102 is mounted a one-way clutch 103 of a common design that inherently engages and rotates a film advance roller 104, but only when the shaft 102 is rotated counterclockwise (as viewed in FIG. 7) by the lever 94. The shaft 102 rotates counterclockwise when the head 74 is being raised, and clockwise when the head is being lowered. Also, the one-way clutch 103 inherently does not engage the film advance roller 104 as soon as thev pinion gear 101 is rotated counterclockwise by the lever 94. Therefore, the head 74 is able to lift the film 21 off the master 16 before the film is advanced. The one-Way clutch y103 does not engage the roller 104 when the shaft 102 rotates clockwise. A ratchet assembly (notshown) may be substituted for the one-way clutch 103, but then means have to be provided to cause the lever 94 to rotate slightly clockwise before the ratchet assembly advances the film. A pawl 106 mounted to side plate 84 engages a toothed wheel 107 fixed to roller =104 to prevent the roller 104 from rotating clockwise due to the tension in the film 21.

The film 21 as used in this embodiment of the contact printer has no sprocket holes by which the film advance roller 104 can grip the film. Therefore, the roller 104 has two spaced rubber rings 108 which contact the film near the edges where no microimages are printed. The roller 104 is backed-up by a pinch roller 109 that also has two spaced rubber rings 111 opposite rubber rings 108 to provide a friction drive for the film 21. Since the rubber rings 108 and 111 contact the film near the edges, the possibility of the rollers scratching the film where the microimages are located is eliminated. The pinch roller 109 is disposed to rotate within two bearing blocks 112 that, in turn, are slidably mounted with lrespect to side plates 83 and 84, and are suitably urged toward the roller 104 by thumb screws 110. The one-way clutch 103 and the rollers 104 and 109 allow the film to advance in equal increments every time the head 74 moves up. A belt 113 (see FIG. 8) that engages pulleys 114 and 116 fixed to the roller 104 and a shaft 117, respectively, causes the reel 51 to rotate and take up the film 21 as required.

Before the film 21 is advanced, the film 21 not only should be lifted perpendicularly off the master 16, but should also be separated from the pressure plate 31 so that neither the master 16 nor the film 21 is scratched as the film is advanced. The film lifters 92 and 93 perform this function. Referring to FIG. l0, there is shown an enlarged elevation of the film lifter 93. The film lifter 92 is similar to lifter 93. The film 21 is held near its edges between two rollers 118 and 119 that are bearing-mounted at each end to vertical members 121 of a roller support frame. The members 121 are connected together at the top and bottom by bars 122 and 123, respectively. Each of the vertical members 121 has a tongue 124 that slidably engages a broove in respective blocks 126 fixed to the head 74 (see FIG. 8). Since the `support members can move up and down with respect to the head 74, the roller support frame is held up by two compression springs 127 acting between the top bar 122 and horizontal flange 128 of an angle member bolted to the head. The springs 127 are suitably retained by pins that are fixed to the angle member 128 and that slide through suitable bores in the top member 122. When the head 74 rises, the springs cause the rollers 118 and 119 to -rise and lift the film 21 perpendicularly off the master. The rollers 118 and 119 rise until the top bar 122 contacts lugs 129 fixed to the underside of the mounting plate 79. When the top bar 122 contacts the lugs 129, springs 127 are compressed as the head 74 continues to rise maintaining the rollers 118 and 119 and film 21 stationary. Since the pawl 106 and toothed wheel 107 prevent the take-up roller 104 from -reversing direction, and since the leaf spring 59 brakes the filrn reel 46, the film 21, held under tension and spaced between the pressure plate 31 and the master 16, is ready to be advanced.

Referring to FIG. l1, the pneumatic and electrical control circuits for the automatic step-and-repeat Contact printer are shown schematically. The pneumatic lines include the four-way solenoid operated valve 87 which is -of a standard design. A schematic representation of the valve is used in FIG. l1 in order to more fully illustrate the operation of the printer. Brifiy, a four-way valve operates as follows: Compressed air is supplied by an inlet tube 131 into a cylindrical bore formed in a valve body 132. Within the bore is slidably disposed a plunger 133 which directs the compressed air to one of the two tubes 88 and 89, depending on the position of the plunger 133 within the valve body 132. Withthe plunger 133 positioned as shown, compressed air is piped into tube 89 to cause the pressure plate 31 to rise. The plunger 133 is coupled through suitable magnetic means to two solenoids 136 and 137 disposed on opposite ends of the valve body 132. The plunger 133 is attracted to the particular solenoid that was last to be energized. For example, when solenoid 136 is energized, the plunger 133 slides toward the solenoid 136 to pipe compressed air into tube 88 and lower the pressure plate 31. The plunger stays in that position until solenoid 137 is energized moving the plunger 133 back to the position as shown in the drawings.

A description of the automatic operation of the contact printer follows. With the pressure plate 31 in the raised position, the film 21 is threaded through the printer. Also, the master 16, back-up plate 37, and pressure plate 32 are placed on the bed 64 in the manner described above. The automatic printing operation is started by closing a hand switch 138. Because the pressure plate 31 is in the raised position, a microswitch 139 is closed, since it is mounted under the mounting plate 79 (see FIG. With the microswitch 139 closed, solenoid 136 is energized. As described in the preceding paragraph, when solenoid 136 is energized, the plunger 13 is attracted to the solenoid 136 and remains in that position even after solenoid 136 is de-ener-gized. With the plunger 133 moved to the position that is alternate to the position shown in FIG. 11, valve 87 directs compressed air from tube 131 into tube 88 to cause the piston to lower the pressure plate 31. When the pressure plate 31 moves down, microswitch 139 opens.

When the pressure plate 31 reaches the bottom of its stroke and the back-up plate 37 is forced into a bowed position as shown in FIG. 5, a microswitch 141 is closed. When switch 141 is closed, a circuit is completed through the contact delay timer 52. The contact delay timer 52 keeps time from when microswitch 141 is closed and the back-up plate 37 is bowed. About two seconds later, which is sufficient time to ensure that the stresses set up in the compressed emulsion coating 23 on the film have balanced out, thus assuring that the emulsion particles do not move relative to each other, even minutely, during or after exposure of the film, the timer 52 closes a switch 142 and holds it closed. When switch 142 is closed, the shutter timer 53 closes a switch 143 to energize a rotary solenoid 144. A shutter 146 is rotated by the solenoid 144 and the light rays from a light source 147 (FIG. 7) expose the film 21 in a manner to be described hereinafter. After allowing sufficient time to expose the film, for example one second, the shutter timer 53 opens switch 143. Also, when the contact delay timer 52 has closed switch 142, the lift delay timer 54 is energized so that the lift delay timer 54 waits until after the shutter timer 53 opens switch 143 before closing a switch 148. Lift delay timer closes switch 148, for example, 1.2 seconds after switch 142 was closed by contact delay timer 52. Therefore a two-tenths of a second tolerance error is provided to ensure that the film 21 is not being exposed while the pressure plate 31 is being raised. When the lift delay timer 54 has closed switch 148, the solenoid 137 is energized (as switch 141 is still closed) to attract the plunger to the position as shown in FIG. 11 so that compressed air is directed through tube 89 to the cylinder to cause the piston to lift the pressure plate 31. In turn, the switch 141 opens, and the timers 52 and 54 are de-energized to open switches 142 and 148, respectively. While the pressure plate 31 is being raised, the film 21 is lifted off the master 16 by the film lifters 92 and 93 and is advanced by the take-up mechanism 49 in the manner heretofore described. When pressure plate 31 reaches its top-most position, microswitch 139 is closed and the -cycle is repeated.

As mentioned in the preceding paragraph, the film is exposed to the light source 147 when switch 143 is closed and, in turn, the rotary solenoid 144 rotates the shutter 146. Referring to FIG. 7, the shutter 146 is located near a pin-hole mask 149,and when solenoid 144 rotates the shutter 146, the light rays from a lamp 151 are focused onto the pin-hole in the mask 149 by a suitable condensing lens system 152. The light rays that pass through the pin-hole approximate a point light source. A lens 153 collects the light rays passing through the pin-hole mask 149 and forms a substantially collimated or semispecular light beam. The collimated light beam is refiected by a mirror 154 toward the master 16 and film 21. The mirror 154 is continuously wobbled through a small angle by a motor and gearing means 156 so that any areal intensity variations in the light rays are averaged over tthe area of the film to expose the Afilm evenly.

The contact printer can also be used to form high resolution contact prints on photographic glass instead of on photographic film. Only one print at a time can be made on photographic glass because the film supply mechanism and the film take-up mechanism as described in this embodiment are not usable with photographic glass. To make contact prints on photographic glass so that high resolution microimages are printed thereon, the pressure plate 32 and back-up plate 37 are pulled out from under the pressure plate 31. Preferably a glass master with a photochromic coating is placed on the ba-ck-up plate 37 and a silver halide photographic glass is placed on the photochromic master with the coatings touching. Since the glass is relatively brittle, a piece of felt cloth is placed on the photographic glass so that the convex surface 33 on the pressure plate 31 contacts the felt cloth, and the cloth evenly distributes the pressure to prevent the glass from breaking. Again since intimate contact is initially formed at the center of the master, air is laterally forced out from between the emulsions as the glass plates bend to the shape of the surfaces 33 and 34. Since the air has a means to escape, no air pockets are formed at the interface of the coatings. The resolution obtainable on photographic glass is inherently better than on lm, because the coating thereon is more evenly distributed. After developing and fixing, a contact print on glass can be used as a master to make contact prints on photographic film.

It is to be understood that a non-automatic contact printer can be made using the teachings of this invention and still be able to consistently produce contact prints having high resolution microimages thereon. Therefore, various other embodiments and variations of the present invention are contemplated and will become apparent to those skilled in the art without departing from the spirit and s-cope of the invention. The invention is not limited to the exemplary apparatus and procedures described, but includes all embodiments within the scope of the claims.

What is claimed is:

1. A photographic contact printer capable of printing high resolution images comprising: two pressure plates, one of said pressure plates having a convex surface and the other of said pressure plates having a concave surface; said pressure plate with the concave surface having an opening for the passage of light rays; a bendable, bend resisting transparent, back-up plate that is normally fiat relative to the curvature of the convex and concave surfaces disposed on said concave surface and over said opening, said transparent plate being of a size to cover the opening such that the edges of the plate can be engaged by the concave surface; a master containing high resolution images disposed on said back-up plate; a substrate provided with a coating of photographic emulsion disposed on said master; means for forcing the two pressure plates together with said back-up plate, said master, and said substrate sandwiched therebetween t0 cause said convex surface to apply pressure to said substrate initially in a small area which area increases outwardly as said back-up plate yields and becomes bowed so as to conform to the contour of said convex surface, said concave surface providing continuous support along the curvature of the conformed back-up plate to support the back-up plate against further bowing whereby said force is applied uniformly over the contacting area of the master and substrate; and a light source disposed to shine light rays through said opening to expose said photographic emulsion after said back-up plate is bowed to placed said photographic emulsion and said master in full contact.

2. A photographic Contact printer for contact printing high resolution images onto a photographic lm from a master negative containing apparent high resolution images, said printer comprising: two pressure plates, one of said pressure plates having a smooth, metallic convex surface and the other of said pressure plates having a concave surface and an opening for the passage of light rays; a bendable, bent resisting transparent back-up plate that is normally flat relative to the curvature of the convex and concave surfaces disposed for covering said opening, said transparent plate being of a size to cover the opening such that the edges of the plate can be engaged by the concave surface; and means for forcing the two pressure plates together with said back-up plate, said master negative, and said film sandwiched therebetween so that said smooth, metallic convex surface contacts said film to cause said film initially to contact said master negative over a small area at the center and to cause the Contact area to increase outwardly to the edges of the master negative as the force exerted by said means increases to thereby bow said back-up plate to conform to the convex surface of said pressure plate, said concave surface providing continuous support along the curvature of the conformed back-up plate to support the back-up plate against further bowing whereby said force is applied uniformly over the contacting area of the master and film.

3. A step-and-repeat contact printer for repeatedly contact printing high resolution images onto a roll of photographic film from a master negative containing high resolution images, said printer comprising: a bed; a frame mounted on said bed; a film feeding mechanism mounted to said frame and disposed to hold the roll of photographic film; a film take-up mechanism mounted to said frame and disposed to take up the roll of film after it is exposed; a stationary pressure plate having a cylindrical concave bearing surface mounted to said bed and between said film feeding mechanism and said take-up mechanism; a movable pressure plate movably mounted to said frame; means mounted to said frame for moving said movable pressure plate toward and away from said stationary pressure plate; said movable pressure plate having a cylindrical convex surface with a radius of curvature generally similar to the radius of curvature of the concave bearing surface facing said stationary pressure plate; said stationary pressure plate and said bed having aligned openings for the passage of light rays to expose said film; a bendable, bend resisting transparent back-up plate that is normally fiat relative to the curvature of the convex and concave surfaces and disposed on said stationary pressure plate over said opening for supporting said master negative, said transparent plate being of a size to cover the opening such that the edges of the plate can be engaged by the concave surface; means disposed to pass said roll of film from said feeding mechanism, in between said master negative and said movable pressure plate, to said take-up mechanism so that when said means for moving said movable pressure plate forces said movable pressure plate toward said stationary pressure plate said convex surface causes the film to initially contact said master negative at a small area near the center and, as the force increases, the area in contact increases outwardly to the edges of the master and said transparent back-up plate bows to conform to said convex surface, said concave surface providing continuous support along the curvature of the conformed back-up plate to support the back-up plate against further bowing whereby said lforce is applied uniformly over the contacting area of the master and film; and mechanical linkage means responsive to the movable pressure plate away from the stationary pressure plate for separating the film from said master negative and then from said convex surface, and actuating means responsive to the moving of the movable pressure plate to actuate said take-up mechanism to advance said film after said film separates from said master and convex surface.

4. A photographic contact printer capable of printing high resolution images comprising: pressure means including a first pressure plate having a smooth rigid convex bearing surface and a second pressure plate having a smooth rigid concave bearing surface, said concave and convex bearing surfaces having substantially similar radii of curvature and one of said bearing surfaces having a central light-transmitting area; means for positioning a bendable, bend resisting transparent plate that is normally flat relative to the curvature of the convex and concave bearing surfaces, a photographic master, and a photographic film between the convex and concave bearing surfaces, said transparent plate being of a size to cover the central light-transmitting area such that the edges of the plate can be engaged by the convex and concave bearing surfaces; means to force the bearing surfaces together to form the said positioned transparent plate, master, and film into the shape of the bearing surfaces whereby the forming pressure is initially along a narrow line transverse to the curvature of the bearing surfaces in the central area of the film and which forming pressure spreads outwardly therefrom to squeeze air out from between the film and master, said concave surface providing continuous support along the curvature of the formed transparent plate to support the transparent plate against further bowing whereby said force is applied uniformly over the contacting area of the master and film; and means for directing light through said central light-transmitting area of one of the bearing surfaces to light expose the film through an image carried by the master.

References Cited by the Examiner UNITED STATES PATENTS 1,929,816 10/1933 Hanson 95-73 2,583,342 1/1952 Reeves 95-75 2,747,457 5/1956 Wengel 352-184 2,826,976 3/1958 Gelb 95-76 2,947,233 8/ 1960 Hickey et al. 95-75 3,016,002 l/1962 Frantz et al. -77 X JULIA E. COINER, Primary Examiner. 

1. A PHOTOGRAPHIC CONTACT PRINTER CAPABLE OF PRINTING HIGH RESOLUTION IMAGES COMPRISING: TWO PRESSURE PLATES, ONE OF SAID PRESSURE PLATES HAVING A CONVEX SURFACE AND THE OTHER OF SAID PRESSURE PLATES HAVING A CONCAVE SURFACE; SAID PRESSURE PLATE WITH THE CONCAVE SURFACE HAVING AN OPENING FOR THE PASSAGE OF LIGHT RAYS; A BENDABLE, BEND RESISTING TRANSPARENT, BACK-UP PLATE THAT IS NORMALLY FLAT RELATIVE TO THE CURVATURE OF THE CONVEX AND CONCAVE SURFACES DISPOSED ON SAID CONCAVE SURFACE AND OVER SAID OPENING, SAID TRANSPARENT PLATE BEING OF A SIZE TO COVER THE OPENING SUCH THAT THE EDGES OF THE PLATE CAN BE ENGAGED BY THE CONCAVE SURFACE; A MASTER CONTAINING HIGH RESOLUTION IMAGES DISPOSED ON SAID BACK-UP PLATE; A SUBSTRATE PROVIDED WITH A COATING OF PHOTOGRAPHIC EMULSION DISPOSED ON SAID MASTER; MEANS FOR FORCING THE TWO PRESSURE PLATES TOGETHER WITH SAID BACK-UP PLATE, SAID MASTER, AND SAID SUBSTRATE SANDWICHED THEREBETWEEN TO CAUSE SAID CONVEX SURFACE TO APPLY PRESSURE TO SAID SUBSTRATE INITIALLY 